Formation And Distribution Of Multi Scale Remaining Oil Based On Physical Simulation Experiment

Most oilfields in China have generally entered the stage of high(ultra-high)water cut in the middle and late stage of development.The reservoir heterogeneity and the distribution of remaining oil are becoming more and more complex.At this stage,Traditional static reservoir characterization and macro remaining oil research methods can not completely solve the problem of remaining oil distribution.It is necessary to explore the formation process of remaining oil combined with physical simulation.In this paper,the braided river reservoir of Guantao Formation in Nanpu area of Jidong Oilfield is taken as the research object,and the formation and distribution of remaining oil are studied by multi-scale water flooding physical simulation experiment,fully considering the reservoir geological factors and development factors that affect the distribution of remaining oil.The achievements and understandings are as follows:(1)The multi-scale remaining oil physical simulation experiment method based on the geological model of strong heterogeneous reservoir from the actual work area is formed,and the coupling of macro and micro scale remaining oil simulation is realized by taking the lithofacies as the connection.(2)The results show that the permeability of the reservoir increases obviously and the heterogeneity of micro pore throat increases before and after water flooding.The characteristics of reservoir and remaining oil are controlled by sedimentary microfacies and lithofacies.(3)2D and 3D physical simulation experiment schemes of remaining oil is constructed,which considers the combination pattern of interlayer,sand body and their matching relationship with well pattern and development measures in macro scale.Compared with the multi-stage superimposed double interlayer core bank model,the core bank model with low permeability single interlayer has longer water free oil recovery period and higher final displacement efficiency in the process of water flooding;Increasing water injection rate,plugging the middle and lower part of water flooded zone and drilling simulated horizontal wells can improve the effective production of remaining oil.(4)One-dimensional physical simulation experiment scheme of remaining oil is constructed,which combines the displacement experiment of remaining oil with reservoir analysis and testing in different displacement stages,considering the formation conditions and real core column on the micro scale.The change process of reservoir and remaining oil in the process of water flooding is revealed,and the change characteristics and remaining oil occurrence patterns of different lithofacies reservoirs in the process of water flooding are different,Because of the differences in physical properties,pore throat development degree,viscosity mineral content between medium sandstone and fine sandstone reservoirs before water flooding,the permeability first increases and then decreases in different degrees in the process of water flooding;The displacement efficiency of remaining oil in medium sandstone facies is relatively high,and the remaining oil is mainly composed of colloidal asphalt.(5)Combining the remaining oil physical simulation experiment with the reservoir characteristics of the study area,The suggestions for the macro scale remaining oil development location and micro scale remaining oil displacement are put forward.The research results of this paper provide method support and theoretical basis for tapping the remaining oil potential and improving the oil and gas displacement efficiency in the middle and late development of old oilfields.